Locomotion Control of Cyborg Insects by Charge-Balanced Biphasic Electrical Stimulation.

The integration of electronic stimulation devices with insects in the context of cyborg insect systems has great application potential, particularly in the fields of environmental monitoring, urban surveillance, and rescue missions. Despite considerable advantages compared to the current robot technology, including flexibility, durability, and low energy consumption, this integration faces certain challenges related to the potential risk of charge accumulation caused by prolonged and repetitive electrical stimulations. To address these challenges, this study proposes a universal system for remote signal output control using infrared signals. The proposed system integrates high-precision digital-to-analog converters capable of generating customized waveform electrical stimulation signals within defined ranges. This enhances the accuracy of locomotion control in cyborg insects while maintaining real-time control and dynamic parameter adjustment. The proposed system is verified by experiments. The experimental results show that the signals generated by the proposed system have a success rate of over 76.25% in controlling the turning locomotion of cyborg insects, which is higher than previously reported results. In addition, the charge-balanced characteristics of these signals can minimize muscle tissue damage, thus substantially enhancing control repeatability. This study provides a comprehensive solution for the remote control and monitoring of cyborg insects, whose flexibility and adaptability can meet various application and experimental requirements. The results presented in this study lay a robust foundation for further advancement of various technologies, particularly those related to cyborg insect locomotion control systems and wireless control mechanisms for cyborg insects.

Structure Design and Heat Transfer Performance Analysis of a Novel Composite Phase Change Active Cooling Channel Wall for Hypersonic Aircraft.

Efficient and stable heat dissipation structure is crucial for improving the convective heat transfer performance of thermal protection systems (TPSs) for hypersonic aircraft. However, the heat dissipation wall of the current TPS is limited by a single material and structure, inefficiently dissipating the large amount of accumulated heat generated during the high-speed maneuvering flight of hypersonic aircraft. Here, a convection cooling channel structure of TPS is proposed, which is an innovative multi-level structure inspired by the natural honeycomb. An active cooling channel (PCM-HC) is designed by using a variable-density topology optimization method and filled with phase change material (PCM). Numerical simulations are used to investigate the thermal performance of the PCM-HC wall, focusing on the influence of PCM properties, structural geometric parameters, and PCM types on heat transfer characteristics. The results demonstrate that the honeycomb-like convection cooling channel wall, combined with PCM latent heat of phase change, exhibits superior heat dissipation capability. With a heat flux input of 50 kW/m2, the maximum temperature on the inner wall of PCM-HC is reduced by 12 K to 20 K. Different PCMs have opposing effects on heat transfer performance due to their distinct thermophysical properties. This work can provide a theoretical basis for the design of high-efficiency cooling channel, improving the heat dissipation performance in the TPS of hypersonic aircraft.

A self-locking mechanism of the frog-legged beetle Sagra femorata.

Insect legs play a crucial role in various modes of locomotion, including walking, jumping, swimming, and other forms of movement. The flexibility of their leg joints is critical in enabling various modes of locomotion. The frog-legged leaf beetle Sagra femorata possesses remarkably enlarged hind legs, which are considered to be a critical adaptation that enables the species to withstand external pressures. When confronted with external threats, S. femorata initiates a stress response by rapidly rotating its hind legs backward and upward to a specific angle, thereby potentially intimidating potential assailants. Based on video analysis, we identified 4 distinct phases of the hind leg rotation process in S. femorata, which were determined by the range of rotation angles (0°-168.77°). Utilizing micro-computed tomography (micro-CT) technology, we performed a 3-dimensional (3D) reconstruction and conducted relative positioning and volumetric analysis of the metacoxa and metatrochanter of S. femorata. Our analysis revealed that the metacoxa-trochanter joint is a "screw-nut" structure connected by 4 muscles, which regulate the rotation of the legs. Further testing using a 3D-printed model of the metacoxa-trochanter joint demonstrated its possession of a self-locking mechanism capable of securing the legs in specific positions to prevent excessive rotation and dislocation. It can be envisioned that this self-locking mechanism holds potential for application in bio-inspired robotics.

A Review of Energy Supply for Biomachine Hybrid Robots.

Biomachine hybrid robots have been proposed for important scenarios, such as wilderness rescue, ecological monitoring, and hazardous area surveying. The energy supply unit used to power the control backpack carried by these robots determines their future development and practical application. Current energy supply devices for control backpacks are mainly chemical batteries. To achieve self-powered devices, researchers have developed solar energy, bioenergy, biothermal energy, and biovibration energy harvesters. This review provides an overview of research in the development of chemical batteries and self-powered devices for biomachine hybrid robots. Various batteries for different biocarriers and the entry points for the design of self-powered devices are outlined in detail. Finally, an overview of the future challenges and possible directions for the development of energy supply devices used to biomachine hybrid robots is provided.

Controllable adhesive mechanisms via the internal fibers in soft footpads of honeybees.

The dynamic adhesive systems in nature have served as inspirations for the development of intelligent adhesive surfaces. However, the mechanisms underlying the rapid controllable contact adhesion observed in biological systems have never been adequately explained. Here, the control principle for the unfolding adhesive footpads (alterable contact area) of honeybees is investigated. The footpads can passively unfold, even without neuro-muscular reflexes, in response to specific dragging activity (generating shear force) toward their bodies. This passive unfolding is attributed to the structural features of the soft footpads, which cooperate closely with shear force. Then, the hierarchical structures supported by numerous branching fibers were observed and analyzed. Experimental and theoretical findings demonstrated that shear force can decrease fibril angles with respect to the shear direction, which consequently induces the rotation of the interim contact area of the footpads and achieves their passive unfolding. Furthermore, the decrease in fibril angles can lead to an increase in the liquid pressure within the footpads, and subsequently enhance their unfolding. This study presents a novel approach for passively controlling the contact areas in adhesive systems, which can be applied to develop various bioinspired switchable adhesive surfaces.

Structural stabilization of honeybee wings based on heterogeneous stiffness.

Structural stabilization for a membrane structure under high-frequency vibration is still a recognized problem. In nature, honeybee wings with non-uniform material properties demonstrate excellent anti-interference ability. However, the correlation between the structural stabilization and mechanical properties of insect wings has not been completely verified. Here we demonstrate that the sclerotization diversity partially distinguishes the stiffness inhomogeneity of the wing structure. Furthermore, a wing cross-section model with diversity in elastic modulus is constructed to analyze the effect of stiffness distribution on stress optimization during flight. Our results demonstrate that the heterogeneous stiffness promotes the stress distribution and structural stabilization of the wing during flight, which may inspire more optimal designs for anisotropic high-strength membrane structures.

Behavioral control and changes in brain activity of honeybee during flapping.

INTRODUCTION: Insect cyborg is a kind of novel robot based on insect-machine interface and principles of neurobiology. The key idea is to stimulate live insects by specific stimuli; thus, the flight trajectory of insects could be controlled as anticipated. However, the neuroregulatory mechanism of insect flight has not been elucidated completely at present. METHODS: To explore the neuro-mechanism of insect flight behaviors, a series of electrical stimulation was applied on the optic lobes of semi-constrained honeybees. Times of flight initiation, flapping frequency, and duration were recorded by a high-speed camera. In addition, flapping and steering initiation experiments of the cyborg honeybee were verified. Moreover, series of local field potential signals of optic lobes during flapping were collected, pre-processed to remove baseline wander and DC components, then analyzed by power spectrum estimation. RESULTS: A quantitative optimization method and optimal stimulation parameters of flight initiation were presented. Stimulation results showed that the flapping duration differed greatly while the flapping frequency varied with little difference among different individuals. Moreover, there was always a fluctuation peak around 20-30 Hz in power spectral density (PSD) curves during flapping, distinguishing from calm state, which indicated some brain activity changes during flapping. CONCLUSIONS: Our study presented a range of relatively optimal electrical parameters to initiate honeybee flight behavior. Meanwhile, the regularity of flapping duration and flapping frequency under electrical stimulations with different parameters were given. The feasibility of controlling a honeybee's flight behavior by brain electrical stimulation was verified through the flapping and steering initiation experiment of honeybees under semi-constrained state. PSD fluctuations reflected changes in brain activity during flapping and that those fluctuation characteristics at the specific frequency band could be sensitive determinants to distinguish whether the honeybee was flying or not, which benefits our understanding of honeybee's flapping behavior and furthers the study of honeybee cyborgs.

Nectar Feeding by a Honey Bee's Hairy Tongue: Morphology, Dynamics, and Energy-Saving Strategies.

Most flower-visiting insects have evolved highly specialized morphological structures to facilitate nectar feeding. As a typical pollinator, the honey bee has specialized mouth parts comprised of a pair of galeae, a pair of labial palpi, and a glossa, to feed on the nectar by the feeding modes of lapping or sucking. To extensively elucidate the mechanism of a bee's feeding, we should combine the investigations from glossa morphology, feeding behaviour, and mathematical models. This paper reviews the interdisciplinary research on nectar feeding behaviour of honey bees ranging from morphology, dynamics, and energy-saving strategies, which may not only reveal the mechanism of nectar feeding by honey bees but inspire engineered facilities for microfluidic transport.

Hairy-Layer Friction Reduction Mechanism in the Honeybee Abdomen.

Abdominal sections of honeybees undergo numerous reciprocating motions during their lifetime. However, the overlapped contact areas adjacent to the abdominal sections have a shallow wear extent, a physical mechanism that remains obscure to date. Therefore, this study explored a biofrictional reduction model based on a solid surface texture and the hairy surface of the honeybee abdomen. We collected honeybee samples and observed their abdomens using a camera (Zeiss Stemi 508). Subsequently, we sliced these samples using a microtome and detected their microscopic friction. The exterior surface of the honeybee abdomen was not smooth but was distributed with a dense microvilli structure, which played a vital role in adjusting the friction reduction characteristics between the abdominal sections. When the adjacent abdominal sections moved relatively to each other, their upper and lower surfaces were not in direct rigid contact. Briefly, this study shows that the microscale hair arrays on the surface of the posterior abdominal segment can significantly reduce real contact area and friction, which considerably decreases wear or abrasion. The friction reduction mechanism alleviates the abrasion during the relative bending movement and saves a large amount of energy, which is essential for the honeybees' daily activities. This microtexture compliance friction reduction characteristic could be used to fabricate hierarchical surfaces for long-lasting friction reduction mechanisms, which increase the life of soft devices, including soft actuators and hinges.

Parallel Mechanism Composed of Abdominal Cuticles and Muscles Simulates the Complex and Diverse Movements of Honey Bee (Apis mellifera L.) Abdomen.

The abdominal intersegmental structures allow insects, such as honey bees, dragonflies, butterflies, and drosophilae, to complete diverse behavioral movements. In order to reveal how the complex abdominal movements of these insects are produced, we use the honey bee (Apis mellifera L.) as a typical insect to study the relationship between intersegmental structures and abdominal motions. Microstructure observational experiments are performed by using the stereoscope and the scanning electron microscope. We find that a parallel mechanism, composed of abdominal cuticle and muscles between the adjacent segments, produces the complex and diverse movements of the honey bee abdomen. These properties regulate multiple behavioral activities such as waggle dance and flight attitude adjustment. The experimental results demonstrate that it is the joint efforts of the muscles and membranes that connected the adjacent cuticles together. The honey bee abdomen can be waggled, expanded, contracted, and flexed with the actions of the muscles. From the view point of mechanics, a parallel mechanism is evolved from the intersegmental connection structures of the honey bee abdomen. Here, we conduct a kinematic analysis of the parallel mechanism to simulate the intersegmental abdominal motions.

Electroantennogram reveals a strong correlation between the passion of honeybee and the properties of the volatile.

INTRODUCTION: Insects use their antennae to detect food, mates, and predators, mainly via olfactory recognition of specific volatile compounds. Honeybees also communicate, learn complex tasks, and show adaptable behavior by recognizing and responding to specific odors. However, the relationship between the electroantennogram and the passion of honeybee has not been determined. METHODS: We established a four-channel maze system to detect the degree of sensitivity of the honeybee's antenna to different odors. In addition, electroantennography (EAG) signal was recorded from the right antennae of the honeybees in our experiments to explore electrophysiological responses to different volatiles. RESULTS: The olfactory sensilla on the antennae of honeybees engender distinct electrophysiological responses to different volatiles. The bees were exposed to honey, 1-hexanol and formic acid, and EAG parameters like depolarization time, falling slope, and amplitude were measured. The EAG indicators varied significantly between honey and formic acid, indicating either "happy" or "anxious" moods. CONCLUSIONS: Honeybee can express its passion by the characteristic changes of EAG parameters. We defined a preference factor (F) to quantify the preference of bees to varying concentrations of different compounds, where greater positive values indicate an increased passion. Our findings provide novel insights into the understanding of odor recognition in insects.

Kinematics of Stewart Platform Explains Three-Dimensional Movement of Honeybee's Abdominal Structure.

The Stewart platform is a typical parallel mechanism, used extensively in flight simulators with six degrees of freedom. It is rarely found in animals and has never been reported to regulate and control physiological activities. Now an equivalent Stewart platform structure is found in the honey bee (Hymenoptera: Apidae: Apis mellifera L.) abdomen to explain its three-dimensional movements. The stereoscope and scanning electron microscope are used to observe the internal structures of honeybees' abdomens. Experimental observations show that the muscles and intersegmental membranes connect the terga with the sterna and guarantee the honey bee abdominal movements. From the perspective of mechanics, a Stewart platform is evolved from the lateral connection structure of the honey bee abdomen, and the intrasegmental muscles between the sternum and tergum function as actuators between planes of the Stewart platform. The extraordinary structure provides various advantages for a honey bee to complete a variety of physiological activities. This equivalent Stewart platform structure can also be used to illustrate the flexible abdominal movements of other insects with the segmental abdomen.

Abdominal pumping involvement in the liquid feeding of honeybee.

Honeybee drinking is facilitated by a "mop-like" tongue, which helps honeybees suck in the sucrose solution from the environment. However, the liquid-transport mechanism from the pharynx to the crop, especially the natural link between abdominal pumping and dipping behavior on the sucrose solution intake, remains obscure. A significant increase in abdominal pumping frequency is observed when honeybees drink the sucrose solution. Abdominal pumping exhibits a function other than respiration. This second function assists in driving the sucrose solution from the pharynx to the crop. We combine the experimental measurements using high-speed video and X-ray phase contrast imaging with theoretical modeling to investigate the effect of abdominal pumping in liquid feeding of honeybee. Experimental results show that a honeybee performs abdominal pumping in the abdomen at a faster rhythm during sucrose solution feeding than during other physiological activities. In addition, the period of abdominal pumping is in concordance with that of dipping cycles. Theoretical analysis demonstrates that the abdomen, which is comparable with a micro pump, changes its volume rhythmically. Such expansion reduces pressure in the abdomen, which also reduces pressure in the crop and helps propel the sucrose solution from the pharynx to the crop. Abdominal pumping can help honeybees improve their feeding efficiency and save foraging time. This research work reveals a specific feeding mechanism of insects fed on sucrose solution and opens a new way for the design of microfluidic pump.

Influence of hydrodynamic pressure and vein strength on the super-elasticity of honeybee wings.

The wings of honeybees (Apis mellifera L.) usually produce bending and torsional deformations during flapping wing movement. These deformations endow honeybees with perfect aerodynamic control to escape predators and exploit scattered resources. However, the mechanisms by which honeybee wings recover from large deformations are unclear. This study demonstrates that honeybee wings are super-elastic that they can recover rapidly from one extreme contorted state to their original position. A comparative experiment is conducted to evaluate the difference in super-elastic recovery between attached and detached wings. Results show that the structural stiffness of wings is affected by the reticulate vein and the haemolymph pressure generated by the blood circulation. Further analysis indicates that the haemolymph pressure can increase the stiffness of honeybee wings, especially that of the subcostal veins. This phenomenon shortens the recovery time of wing deflection behaviour.

Honeybees Prefer to Steer on a Smooth Wall With Tetrapod Gaits.

Insects are well equipped in walking on complex three-dimensional terrain, allowing them to overcome obstacles or catch prey. However, the gait transition for insects steering on a wall remains unexplored. Here, we find that honeybees adopted a tetrapod gait to change direction when climbing a wall. On the contrary to the common tripod gait, honeybees propel their body forward by synchronously stepping with both middle legs and then both front legs. This process ensures the angle of the central axis of the honeybee to be consistent with the crawling direction. Interestingly, when running in an alternating tripod gait, the central axis of honeybee sways around the center of mass under alternating tripod gait to maintain stability. Experimental results show that tripod, tetrapod, and random gaits result in the amazing consensus harmony on the climbing speed and gait stability, whether climbing on a smooth wall or walking on smooth ground.

Critical Structure for Telescopic Movement of Honey bee (Insecta: Apidae) Abdomen: Folded Intersegmental Membrane.

The folded intersegmental membrane is a structure that interconnects two adjacent abdominal segments; this structure is distributed in the segments of the honey bee abdomen. The morphology of the folded intersegmental membrane has already been documented. However, the ultrastructure of the intersegmental membrane and its assistive role in the telescopic movements of the honey bee abdomen are poorly understood. To explore the morphology and ultrastructure of the folded intersegmental membrane in the honey bee abdomen, frozen sections were analyzed under a scanning electron microscope. The intersegmental membrane between two adjacent terga has a Z-S configuration that greatly influences the daily physical activities of the honey bee abdomen. The dorsal intersegmental membrane is 2 times thicker than the ventral one, leading to asymmetric abdominal motion. Honey bee abdominal movements were recorded using a high-speed camera and through phase-contrast computed tomography. These movements conformed to the structural features of the folded intersegmental membrane.

Erection mechanism of glossal hairs during honeybee feeding.

Many animals use their mouthparts or tongue to feed themselves rapidly and efficiently. Honeybees have evolved specialized tongues to collect nectar from flowers. Nectar-intake movements consist of rapid protraction and retraction of glossa from a tube formed by the maxillae and labial palps. We establish a physical model to reveal the driving mechanism of hair erection. Results indicate that the glossa of honeybees is similar to a compression spring. Experimental results show that hair erection is generated by the tension of hyaline rod and the elasticity of segmental sheath. The retractor muscle of hyaline rod is contracted at first, which compresses the sheath of pigmented rings and flattens the hairs. While the retractor muscle of hyaline rod relaxes, the elastic energy storage in the compressed glossal sheath will release to change the equivalent stiffness of glossal sheath and erect glossal hairs. These results explain the erection mechanism of glossal hairs during honeybee feeding.

Movement Analysis of Flexion and Extension of Honeybee Abdomen Based on an Adaptive Segmented Structure.

Honeybees (Apis mellifera) curl their abdomens for daily rhythmic activities. Prior to determining this fact, people have concluded that honeybees could curl their abdomen casually. However, an intriguing but less studied feature is the possible unidirectional abdominal deformation in free-flying honeybees. A high-speed video camera was used to capture the curling and to analyze the changes in the arc length of the honeybee abdomen not only in free-flying mode but also in the fixed sample. Frozen sections and environment scanning electron microscope were used to investigate the microstructure and motion principle of honeybee abdomen and to explore the physical structure restricting its curling. An adaptive segmented structure, especially the folded intersegmental membrane (FIM), plays a dominant role in the flexion and extension of the abdomen. The structural features of FIM were utilized to mimic and exhibit movement restriction on honeybee abdomen. Combining experimental analysis and theoretical demonstration, a unidirectional bending mechanism of honeybee abdomen was revealed. Through this finding, a new perspective for aerospace vehicle design can be imitated.

Barbs facilitate the helical penetration of honeybee (Apis mellifera ligustica) stingers.

The stinger is a very small and efficient device that allows honeybees to perform two main physiological activities: repelling enemies and laying eggs for reproduction. In this study, we explored the specific characteristics of stinger penetration, where we focused on its movements and the effects of it microstructure. The stingers of Italian honeybees (Apis mellifera ligustica) were grouped and fixed onto four types of cubic substrates, before pressing into different substrates. The morphological characteristics of the stinger cross-sections were analyzed before and after penetration by microscopy. Our findings suggest that the honeybee stinger undergoes helical and clockwise rotation during penetration. We also found that the helical penetration of the stinger is associated directly with the spiral distribution of the barbs, thereby confirming that stinger penetration involves an advanced microstructure rather than a simple needle-like apparatus. These results provide new insights into the mechanism of honeybee stinger penetration.